The Media Gateway Controller (MGC) and the Media Gateway (MG) are two key components of a packet-switched network. The MGC is responsible for the call control function, and the MG is responsible for the service bearing function. In this way, the call control plane is separated from the service bearer plane, the network resources are sufficiently shared, the equipment upgrade and the service extension are simplified, and the development and maintenance costs are slashed. FIG. 1 shows a networking structure of the MGC and the MG.
The media gateway control protocol is a main protocol for communication between the MG and the MGC. The currently prevalent media gateway control protocols include H.248/Gateway Control Protocol (H.248/MeGaCo) and Media Gateway Control Protocol (MGCP). The MGCP R1 protocol was formulated by the Internet Engineering Task Force (IETF) in October 1999 and revised in January 2003. The H.248/MeGaCo R1 protocol was formulated jointly by the IETF and the International Telecommunications Union (ITU) in November 2000 and revised in June 2003. The H.248 R2 protocol was formulated by the ITU in May 2002 and revised in March 2004, and the H.248 R3 protocol was formulated by the ITU in September 2005.
In the H.248 protocol, various resources on the MG are abstractly represented by terminations. Terminations are categorized into physical terminations and ephemeral terminations. Physical terminations are physical entities which exist semi-permanently, for example, Time Division Multiplex (TDM) channels. Ephemeral terminations represent the public resources which are requested temporarily and released soon after use, such as, Real-time Transport Protocol (RTP) streams. A root termination is used to represent the entirety of the MG. The combinations among terminations are abstractly represented by contexts. A context may include multiple terminations, and interrelations between terminations described through topologies. A termination not related to other terminations is included in a special context called a “null”.
Based on an abstract model such as the H.248 protocol, the call connection is actually an operation on the terminations and the contexts. Such operations are performed through Command Requests and Reply between the MGC and the MG. The Command types include: Add, Modify, Subtract, Move, Audit Value, Audit Capabilities, Notify, and Service Change. Command parameters, also referred to as descriptors, are categorized into Property, Signal, Event, and Statistic. The parameters with service relevance are logically aggregated into a package.
In the practical application, a physical MG may be divided into one or more Virtual Media Gateway (VMG). A VMG may consist of a set of statically divided physical termination and/or multiple sets of ephemeral termination. A VMG is controlled by only one MGC at a time. For the MGC, each VMG is a complete MG. However, on a physical MG, it is possible that only one or several network interfaces exist, and each network interface may be shared by multiple VMGs. This mechanism may lead to a complicated problem. For example, when an event occurs on this shared interface, the physical MG needs to identify the proper VMG so as to report the detected event to the MGC that controls the physical MG. In this case, it may complicate the selection of a VMG.
Taking the resource control scenario in the H.248.55 as an example, FIG. 2 is a resource control diagram in the VMG scenario. The function entities involved include: User Equipment (UE), Session Control Function (SCF), Resource Admission Control Function (RACF), and Policy Enforcement Entity (PE-E). When the H.248 is used as an interface protocol between the RACF and the PE-E, and the RACF and the PE-E are equivalent to the MGC and MG in the H.248 entity respectively.
The physical MG in FIG. 2 is divided into multiple VMGs, where VMG1 is controlled by MGC1, and VMG2 and VMG3 are controlled by MGC2. Establishing of a session generally includes two parts: signaling negotiation on the service layer, and resource negotiation on the bearer layer. In the signaling negotiation on the service layer, the MGC may generate an authorization token, which includes a Fully Qualified Domain Name (FQDN) of the MGC and a session identifier for the MGC to uniquely identify a resource request on the bearer layer. The authorization token is carried through a signaling message to the UE. The resource negotiation on the bearer layer is initiated by the UE, and the UE sends an event triggering message to the MG. The message may carry the authorization token information. After receiving the event triggering message from the UE, the MG needs to report a Quality of Service (QoS) Request of Deciding Resource Reservation (RDRR) event in the H.248.55 to the MGC that controls the VMG, so as to request the MGC to send a resource provision decision to the MG. In the case of VMG, after receiving the event triggering message from the UE, the physical MG needs to select a proper VMG first, and then report the detected event to the MGC.
For this problem, a solution provided in the prior art is:
The physical MG resolves the VMG information related to the event according to the resource allocation information (for example, context, address and port of the termination) of each current VMG and/or the received message (for example, authorization token in the event triggering message), and then the specific VMG report the detected event to the MGC which controls the VMG.
For example, in the H.248.55 protocol, the resource strategy control comes in two modes: Context-created MG pull mode, and Context-less MG pull mode. In the Context-created MG pull mode, the VMG has created information about the context and the termination. If the event triggering message received by the physical MG includes specific destination information that matches a VMG, the physical MG may report the detected event according to the uniquely determined VMG. In the Context-less MG pull mode, the VMG has not created the relevant context and the termination information. If the event triggering message received by the physical MG carries a parameter (for example, authorization token) that includes VMG selection information, and the physical MG is capable of resolving such information, the physical MG may also select a proper VMG to report the detected event.
However, the information on which the solution depends may be unavailable. For example, in the Context-less MG pull mode, when the carrier event is detected by the physical MG, the VMG may have not created the relevant resource address identifier. The event triggering message received by the physical MG may include no parameter (for example, authorization token, which is an optional parameter in the message) from which VMG information can be resolved; or, even if the event triggering message received in the physical MG includes a parameter from which the VMG information can be resolved, the MG may also be unable to obtain the selection information of the VMG through decoding. Therefore, this solution is not universal, and especially not suitable for the Context-less MG pull mode in the VMG.
In the practical application, the following circumstances may occur:
1. The physical MG receives the indication information such as authorization token and is capable of resolving such information, but such information is incapable of reflecting the selection information (address or identifier) of the VMG and/or MGC.
2. The physical MG receives the indication information such as authorization token, but is incapable of resolving the information, for example, the physical MG does not perceive the authorization token.
3. The physical MG receives no indication information such as authorization token. For example, the bearer event triggering message carries no indication information such as authorization token.
Another solution provided in the prior art is a mode similar to broadcast. That is, when the physical MG receives an event triggering message (for example, resource request message of the bearer layer), all the VMGs on which this event is currently set report the detected event to the MGC that controls the VMG, and then each MGC judges whether it is necessary to apply the corresponding processing measures.
In this solution, the physical MG does not select the specific VMG. Moreover, the quasi-broadcast mode generates plenty of information, increases unnecessary load between the physical MG and the MGC, and affects the working efficiency and performance of the MG and MGC.
Therefore, in the prior art, the physical MG has no proper mechanism for selecting the VMG after receiving the event triggering message.